An interior passenger compartment of an automobile is designed to provide a quiet environment and to protect the driver and passengers from outside elements, such as rain, snow, cold, heat, dust, exhaust fumes, pollution, etc. As such, automobiles typically provide an interior passenger compartment that is substantially sealed from the surrounding exterior environment. However, the air pressure inside the interior passenger compartment may undesirably exceed atmospheric pressure in some instances, for example, when a vehicle door is closed. If the interior is not vented to the atmosphere, the effort required to close the door may greatly increase, inconveniencing the driver or passenger of the vehicle. Deployment of air bags may also cause a sudden increase in internal pressure. Higher internal pressures can also be created by a fan of a climate control system or by the inrush of outside air when a window or sunroof is opened when traveling at high speeds.
Pressure relief valves for equalizing the pressure between the interior compartment of an automobile and the atmosphere are known. The pressure relief valve is placed between the interior space and the outside of the vehicle in order to control an exhaust flow of air from the interior. The pressure relief valve (or “air extractor”) is typically connected by a duct to the passenger compartment. The valve permits air to be expelled or discharged from the vehicle passenger compartment, while preventing air, gas, fumes, and/or other undesirable substances from entering into the passenger compartment. By minimizing overpressure in the passenger compartment, the pressure relief valve improves the performance of the climate control system, makes it easier to close doors, and reduces the unpleasant buffeting noise from open windows. Further performance improvements, particularly to improve flow characteristics through the valve, would be highly desirable. Accordingly, a pressure relief valve with improved aero-acoustic properties would be useful to reduce noise in the passenger compartment.